Partially barricaded by stone walls, accented with Baroque buildings and lying on cobblestone streets, Santo Domingo's Zona Colonial marks the area where Columbus settled in the New World. Visitors say it's definitely a must-see, considering the city's best-known historic sites are located here. But this UNESCO World Heritage Site also shelters many hotels, bars and restaurants. Best of all, you can explore the area entirely on foot: For all that's crammed inside, there's really only 12 blocks worth of sights.

According to a TripAdvisor user: "The great thing about the Zona Colonial is that it is still a genuine community and not overrun with tourists. … It is perfectly safe to walk around during the day and night and with a good map you really don't need the services of a guide."

So where to start? How about the Catedral Primada de América, located near the heart of the zone (look for the statue of Christopher Columbus)? From there you can trek a little farther west to Fortaleza Ozama, located along the mouth of the Río Ozama in the southeast quadrant. Next, walk along the Calle Las Damas (the oldest street, a pedestrian-only zone) to the Alcázar de Colón palace and museum.